U.S. patent number 6,817,987 [Application Number 10/222,677] was granted by the patent office on 2004-11-16 for mixing hypodermic syringe.
This patent grant is currently assigned to Arzneimittel GmbH Apotheker Vetter & Co. Ravensburg. Invention is credited to Thomas Otto, Udo J. Vetter.
United States Patent |
6,817,987 |
Vetter , et al. |
November 16, 2004 |
Mixing hypodermic syringe
Abstract
A syringe holding a solvent and a soluble component has a
tubular body formed its front and rear ends with a bypass, a
plunger axially slidable in the body, and a stem projecting axially
rearward out of the body from the plunger. A cover fits over the
front end of the body and is so tight that the front compartment
can be pressurized to a superatmospheric pressure without leakage
out the front end. A free piston slidable in the body forward of
the plunger subdivides the body forward of the plunger into a front
compartment at the front body end holding the soluble component and
a rear compartment between the plunger and the piston and holding
the solvent. Stops are provided for arresting the free piston when
it is level with the bypass in a position permitting flow through
the bypass between the compartments.
Inventors: |
Vetter; Udo J. (Ravensburg,
DE), Otto; Thomas (Weingarten, DE) |
Assignee: |
Arzneimittel GmbH Apotheker Vetter
& Co. Ravensburg (Ravensburg, DE)
|
Family
ID: |
7695977 |
Appl.
No.: |
10/222,677 |
Filed: |
August 16, 2002 |
Foreign Application Priority Data
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Aug 18, 2001 [DE] |
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101 40 704 |
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Current U.S.
Class: |
604/85;
604/92 |
Current CPC
Class: |
A61M
5/284 (20130101); A61M 2005/31508 (20130101) |
Current International
Class: |
A61M
5/28 (20060101); A61M 5/315 (20060101); A61M
037/00 () |
Field of
Search: |
;604/19,27,28,500,506,507,82,85,89-92,145,181,182,187,191-192,207-208,210-211,218,220-224 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Casler; Brian L.
Assistant Examiner: Thompson; Michael M.
Attorney, Agent or Firm: Dubno; Herbert Wilford; Andrew
Claims
What is claimed is:
1. A syringe comprising: a tubular body extending along an axis and
having a front end and a rear end and formed therebetween with a
bypass; a plunger axially slidable in the body; a stem projecting
axially rearward out of the body from the plunger a cover over the
front end of the body and sufficiently tight to allow
superatmospheric pressurization of the front compartment; a free
piston slidable in the body forward of the plunger and subdividing
the body forward of the plunger into a front compartment at the
front body end holding the soluble medicament and a rear
compartment between the plunger and the piston and holding the
solvent, whereby when the plunger and stem are pressed axially
forward from a rearmost end position into an intermediate position
to pressurize the rear compartment and force the piston forward
until the piston is at the bypass and the solvent can flow through
the bypass into the front compartment to mix with the soluble
medicament with build up of gas pressure in the front compartment;
and stop means for arresting the piston when it is at the bypass
for permitting fluid flow in two directions through the bypass past
the piston while still permitting free axial movement of the
plunger, whereby gas pressure in the front compartment can force
the plunger rearward and pump the solvent and any of the medicament
mixed therewith back past the arrested piston and through the
bypass into the rear compartment.
2. The syringe defined in claim 1 wherein the stop means is
interengageable radially extending formations on the body and
piston.
3. The syringe defined in claim 2 wherein the formations include a
radially inwardly projecting bump on the body and a complementary
radially outwardly open recess on the piston.
4. The syringe defined in claim 1, further comprising means
including stops on the stem and body for inhibiting forward
movement of the plunger past the intermediate position.
5. The syringe defined in claim 4 wherein the stops include
screwthread formations on the stem and body, whereby the stem has
to be rotated about the axis for movement forward past the
intermediate position.
6. The syringe defined in claim 5 wherein the screwthread on the
stem is of limited axial extent.
7. The syringe defined in claim 4 wherein the stops include
screwthread formations on the stem and body, whereby the stem has
to be rotated about the axis for movement forward past the rear end
position.
8. The syringe defined in claim 7 wherein the screwthread on the
stem is of limited axial extent.
9. The syringe defined in claim 4 wherein the stops include at
least one radially projecting bump on the stem and at least one
radially inwardly open notch through which the bump can pass
axially on the body, whereby the stem has to be rotated about the
axis and angularly position for movement forward past the
intermediate position.
10. The syringe defined in claim 4 wherein the stops include at
least one radially projecting bump on the stem and at least one
radially inwardly open notch through which the bump can pass
axially on the body, whereby the stem has to be rotated about the
axis and angularly position for movement forward past the rear end
position.
11. A method of operating a syringe having: a tubular body
extending along an axis and having a front end and a rear end and
formed therebetween with a bypass, a plunger axially slidable in
the body; a stem projecting axially rearward out of the body from
the plunger a cover over the front end of the body; and a free
piston slidable in the body forward of the plunger and subdividing
the body forward of the plunger into a front compartment at the
front body end and a rear compartment between the plunger and the
piston the method comprising the steps, after having provided the
front compartment with a charge of compressible gas and a dose of a
dry soluble medicament and the rear compartment with a liquid
solvent for the medicament and starting with the plunger and stem
in a rearmost end position and the piston at least partially
axially rearward of the bypass and separating the solvent from the
soluble medicament, of: a) pressing the plunger and stem axially
forward from the rearmost end position into an intermediate
position with the plunger rearward of the bypass and thereby
pressurizing the rear compartment and forcing the piston forward
until the piston is at the bypass and the solvent can flow through
the bypass and into the front compartment to mix with the soluble
medicament while maintaining the front end closed such that gas
pressure builds up in the front compartment; b) when the piston is
at the bypass, arresting the piston at the bypass and permitting
fluid flow in two directions through the bypass past the piston;
and c) releasing the plunger and stem such that gas pressure built
up in the front compartment forces the plunger rearward and pumps
the solvent and any of the medicament mixed there-with back past
the arrested piston and through the bypass into the rear
compartment.
12. The syringe-operating method defined in claim 11, further
comprising: stopping forward movement of the plunger and stem in
the intermediate position by engagement between formations on the
plunger and body.
13. The syringe-operating method defined in claim 11, further
comprising the step of d) repeating steps a) and c) while
continuing to arrest the piston at the bypass to pump the solvent
back and forth between the compartments and thereby thoroughly mix
the solvent and medicament.
14. The syringe-operating method defined in claim 11, further
comprising the steps after step c) of sequentially: e) uncovering
the front body end; f) pushing the plunger and stem forward from
the intermediate position and thereby pressing generally all of the
solvent/medicament mixture in the rear compartment into the front
compartment until the plunger rearwardly engages the piston; and g)
pushing the plunger, stem, and piston forward to express the
solvent/medicament mixture out the front end of the syringe body.
Description
FIELD OF THE INVENTION
The present invention relates to a method of mixing a pair of
components, normally a medicament and a solvent. More particularly
this invention concerns such a method and a hypodermic syringe for
carrying out the method.
BACKGROUND OF THE INVENTION
As described in commonly owned U.S. Pat. No. 6,419,656, a medical
syringe has a tubular body extending along an axis and having a
front end and a rear end, a plunger axially slidable in the body
and carrying a stem projecting axially rearward out of the body
from the plunger, and a free piston slidable in the body forward of
the plunger and subdividing the body forward of the plunger into a
front compartment at the front body end and a rear compartment
between the plunger and the piston. The body is formed with a
bypass passage forward of the piston in a starting position so the
front compartment can hold a soluble medicament and the rear
compartment can hold its solvent. Structure at the rear body end
forms a radially inwardly open angularly limited cutout and at
least two axially spaced, angularly offset, and radially outwardly
projecting stop bumps on the stem are axially displaceable through
the cutout in respective angularly offset positions of the stem.
The stop bumps are axially engageable against the structure except
when the stem is in the respective angular position. An elastically
deformable brake element engaged between the body and the stem for
axially slowing axial forward advance of the stem.
Such a system is extremely effective when the medicament is highly
soluble in the solvent. When, however, the medicament is less
soluble, it is necessary for the user to shake the syringe in order
to ensure proper mixing. Such shaking not only is an annoying step,
but also risks damage to the syringe. Furthermore it is inexact at
best, so that often the patient is injected before all the
medicament is fully dissolved, resulting in clogging of the needle
or insufficient dosing.
OBJECTS OF THE INVENTION
It is therefore an object of the present invention to provide an
improved method of mixing a medicament and its solvent.
Another object is the provision of an improved mixing syringe which
overcomes the above-given disadvantages, that is which allows the
user to fully mix even a hard-to-dissolve medicament.
SUMMARY OF THE INVENTION
A syringe holding a solvent and a soluble component has according
to the invention a tubular body extending along an axis and having
a front end and a rear end and formed therebetween with a bypass, a
plunger axially slidable in the body, and a stem projecting axially
rearward out of the body from the plunger. A cover fits over the
front end of the body and is in accordance with the invention so
tight that the front compartment can be pressurized to a
superatmospheric pressure without leakage out the front end. A free
piston slidable in the body forward of the plunger subdivides the
body forward of the plunger into a front compartment at the front
body end holding the soluble component and a rear compartment
between the plunger and the piston and holding the solvent. Stops
are provided for arresting the free piston when it is level with
the bypass in a position permitting flow through the bypass between
the compartments.
This syringe is used according to the invention by, starting with
the plunger and stem in a rearmost end position and the piston at
least partially axially rearward of the bypass and separating the
solvent from the soluble component, first pressing the plunger and
stem axially forward from the rearmost end position into an
intermediate position with the plunger rearward of the bypass and
thereby pressurizing the rear compartment and forcing the piston
forward until the piston in at the bypass and the solvent can flow
through the bypass and into the front compartment to mix with the
soluble component while gas pressure builds up in the front
compartment. When the piston is at the bypass, it is arrested to
permit fluid flow in two directions through the bypass past the
piston. Then the plunger and stem are released such that gas
pressure built up in the front compartment forces the plunger
rearward and pumps the solvent and any of the component mixed
therewith back through the bypass into the rear compartment.
This pressing and releasing can be done several times to pump the
solvent/component mixture back and forth through the bypass between
the compartments so as to thoroughly mix them. In this manner even
relatively hard-to-dissolve components can be easily and thoroughly
dissolved without having to shake the syringe. Normally only a few
presses and releases are needed even for the most stubborn
substances due to the turbulence of the flow through the bypass
which is of restricted flow cross section.
Forward movement of the plunger and stem is stopped in the
intermediate position by engagement between formations on the
plunger and body. These formations can include short screwthreads
on the stem and a short screwthreaded area on the body so that the
body must be rotated to advance it forward out of the rearmost
position, and then rotated again after mixing is complete to
advance it forward from the intermediate position. Instead of
screwthreads, bumps can be provided on the stem at angularly and
axially offset positions so that the stem has to be twisted to fit
the bumps through a notch in the body, such twisting being needed
to advance forward from the rear end position and again from the
intermediate position.
Once the soluble component in the front compartment is thoroughly
mixed with the solvent, according to the invention the front body
end is uncovered and fitted with a needle and then the plunger and
stem are pushed forward from the intermediate position to press
generally all of the solvent/component mixture in the rear
compartment into the front compartment until the plunger rearwardly
engages the piston. Further forward advance of the plunger, stem,
and piston expresses the solvent/component mixture out the front
end of the syringe body.
BRIEF DESCRIPTION OF THE DRAWING
The above and other objects, features, and advantages will become
more readily apparent from the following description, reference
being made to the accompanying drawing in which:
FIG. 1 is an axial section through a syringe for carrying out the
method of this invention;
FIG. 2 is a view like FIG. 1 at the start of a mixing
operation;
FIG. 2A in a large-scale view of the detail indicated at IIA in
FIG. 2;
FIGS. 3, 4, 5, and 6 are views like FIG. 1 illustrating further
steps in the operation of the syringe of FIG. 1;
FIG. 7 is a view like FIG. 1 of another syringe in accordance with
the invention;
FIG. 7A is a section taken along line VIIA--VIIA of FIG. 7;
FIG, 7B is a large-scale view of the detail indicated at VIIB in
FIG. 7; and
FIGS. 8 through 13 are views like FIG. 7 showing use of the FIG. 7
syringe.
SPECIFIC DESCRIPTION
As seen in FIG. 1, a syringe 1 has a basically tubular glass or
plastic body 3 centered on an axis A and slidably receiving a
plunger 6. A rod or stem 5 projects axially rearward from the
plunger 6 through a finger-brace end cap 7. A free piston 8
subdivides the tubular body 3 forward of the plunger 6 into a front
compartment 2 that is to start with filled with gas and a soluble
medicament, normally in lyophilized powder form, and a rear
compartment 4 that to start with is filled with a liquid solvent
for the medicament. A radially inwardly open and axially extending
bypass groove 9 is formed in the tubular body 3 forward of the
piston 8 in the FIG. 7 starting position. Initially the front end
of the tubular body 3 is covered by a cap 11 which is replaced for
use by a needle or cannula 17 (FIG. 6). The rear end of the tubular
body 3 is formed with a short internal screwthread 16 and the stem
5 is formed with a complementary front external screwthread 12 and
a similar rear external screwthread 13.
According to the invention the syringe body 3 is formed with an
internal stop bump 10 shown in FIG. 2A and adapted to fit in a
complementary outwardly open recess or groove of the piston 8 when
same is in a position sitting generally centrally in the bypass 9.
In addition the piston 8 has an axial length substantially shorter
than the bypass 9 so that, when arrested by the stop 10, fluid can
flow axially past it through the bypass 9, which can be formed by
several axially extending and radially inwardly open grooves. Also
according to the invention the cap 11 is constructed such that it
can withstand considerable pressure, allowing the front compartment
2 to be pressurized at a significant superatmospheric pressure.
This is typically achieved by making it a two-part structure, with
a holding ring 18 that must be broken and removed before the cap
11, which secures in place an unillustrated elastomeric plug, can
be stripped off.
In accordance with the invention the syringe 1 starts in the
position shown in FIG. 1. The front screwthread 12 of the stem 5 is
threaded with the rear-end body screwthread 16 and the plunger or
rear plunger 6 is retracted to the extreme rear end of the body 3.
The front piston 8 is positioned axially somewhat rearward of the
bypass 9 no that the lyophilized dry medicament in the front
compartment 2 is completely separated from the aqueous solvent in
the rear compartment.
To start with the stem 5 is rotated to move the screwthread 12
axially forward through the screwthread 16 and then the plunger 6
and stem 5 are advanced as shown in FIG. 2. The relatively
incompressible solvent in the rear compartment 4 pushes the piston
8 forward until it is in the middle of the bypass 9 and the stop
bump 10 arrests it, whereupon the solvent flows through the bypass
into the front compartment 2. This action compresses the sterile
gas in the front compartment 2 and mixes the solvent with the
medicament as shown by the dashed-line/solid-line hatching. Forward
movement of the piston 8 and stem 5 is stopped when the rear stem
screwthread 13 axially abuts the body screwthread 16.
The user then releases the stem 5 so that the pressure in the front
compartment 2 forces the contents of this compartment 2 back
through the bypass into the rear compartment 4 as indicated in FIG.
3, further mixing the solvent and the medicament. The user then
advances the stem 5 again as shown in FIG. 4 to pump the mixture
(still shown in dashed-line/solid-line hatching) forward into the
front compartment 2 and dissolve even more of the medicament. This
process is repeated until as shown in FIG. 5 all of the medicament
is dissolved. Forcing the solvent back and forth through the
constriction constituted by the bypass 9 very effectively mixes the
solvent and medicament, so that normally only a few presses on the
stem 5 are needed to thoroughly mix them.
Finally the cap 11 is removed and replaced with a standard
Luer-type needle or cannula 17 as shown in FIG. 6 while the stem 5
and plunger 6 are in their rear end positions so that the
compartment is generally depressurized or at atmospheric pressure.
The stem 5 is then rotated to move the screwthread 13 forward
through the screwthread 16, whereupon the plunger 6 can be pressed
against the rear end of the piston 8 to express the mixture from
the cannula 17. The total axial length of the pistons 6 and 8 is
greater than that of the bypass 9 so that this can be done with no
significant loss or leakage backward of the mixture. Once emptied,
the unit is discarded.
In FIGS. 7 through 18 an arrangement is shown which has, instead of
the screwthread 12, 13, and 16, three axially spaced sets of
radially projecting bumps 14 on the stem 5 and inwardly projecting
ribs defining complementary radially inwardly open notches 15 in
the rear body end. Thus starting from the position of FIGS. 7 and 8
the stem 5 has to be rotated to fit the frontmost set of bumps 14
through the notches 15 to allow pumping and mixing in the position
of PIGS. 9 through 12 with the middle set of bumps 14 limiting
forward advance of the stem 5. Then the stem 5 is rotated again
after mixing of the syringe contents as shown in FIG. 13 to allow
the middle set of bumps 14 to pass through the notches 15 and allow
expressing of the mixed contents. Once the syringe is emptied, the
stem 5 is twisted again to lock the rearmost set of bumps 14
forward of the notches 15.
* * * * *